Investigation of DNA damage and repair kinetics in normal and tumor tissue may lead to the development of therapy schedules that will take advantage of the differences in these kinetics to improve a tumor patient's response. Because tumors of the central nervous system are essentially dividing populations of cells within a predominantly nondividing normal tissue, differences in their DNA damage and repair kinetics are likely to occur. Therefore, we are proposing to apply the recently developed technique of viscoelastometry to investigate the DNA damage and repair kinetics of normal rat brain and the intracerebral rat 9L brain tumor after treatment with radiation and chemotherapeutic agents. Initially we will build a viscoelastometer, then characterize the DNA species responsible for generating the viscoelastic retardation signals, investigate the DNA damage and repair kinetics of cultured rat 9L brain tumor cells after treatment with radiation and chemotherapeutic agents and finally evaluate the DNA damage and repair kinetics of the normal rat cerebellum and intracerebral rat 9L brain tumor after in vivo treatment with radiation and chemotherapeutic agents. These results combined with those obtained from our studies with slow reorienting zonal rotor techniques should allow rational development of brain tumor therapy schedules based on differences between the posttreatment DNA kinetics of normal and tumor tissue.